I'm not discounting the fact that some Toshiba tech may be in some of the sensors that have a Toshiba name printed on it but Toshiba don't need to make a bespoke fab facility to create an entirely Nikon designed sensor. Just like TSMC don't make a dedicated facility just for Nvidia as An Exception points out. Silicon wafers are produced and fabbed, there is then some assembly into the packaged chip with the other components (read out lines, power circuitry, filtering etc.). This outer packaging is most likely what the Nikon design has to conform to facilitating easy production with existing facilities at the plant. The silicon design could be anything that is supported by the facility.